test: add musl-libc testsuite

[inkydragon]

Do NOT merge with squash commits!

• make coverage will run glibc and musl test, and then gen report.
  • Currently, it passes all musl tests under linux CI.
    Other platforms have not been tested yet. Wait for the following pr
• make test will only run glibc test.
  • TODO: run musl test on win and mac CI
• All modifications are marked with XXX.
• Tests that are currently skipped are marked with TODO.
  • Some tests were moved to subfolders to skip them
    src\math\broken\*, src\math\not-impl\*

Since there are a lot of new files added, it is recommended to review the changes made after the addition of new tests one by one.

---

broken tests:

• fenv
• fma
• fmaf
• fmal
• fpclassify
• j1
• j1f
• jn
• jnf
• nearbyintl
• nextafterl
• nexttoward
• nexttowardl
• round
• tgamma
• yn
• ynf

not impl funcs:

• drem
• dremf
• exp10
• exp10f
• exp10l
• pow10
• pow10f
• pow10l
• scalb
• scalbf

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4b83beb) 38.24% compared to head (4644b62) 68.96%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #298       +/-   ##
===========================================
+ Coverage   38.24%   68.96%   +30.72%     
===========================================
  Files         233      233               
  Lines        6139     6142        +3     
  Branches     1607     1607               
===========================================
+ Hits         2348     4236     +1888     
+ Misses       3394     1596     -1798     
+ Partials      397      310       -87     

☔ View full report in Codecov by Sentry.
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[ViralBShah]

Just thinking out aloud, if the musl libm passes all these tests - would it be best to pull out the libm from musl into a standalone library and update openlibm to that?

[inkydragon]

pull out the libm from musl into a standalone library
and update openlibm to that?

I like this idea.
Moving a step further, we could take the libm related tests from libc-testsuite (for musl)
and put them in a standalone project, maybe call it openlibm-test.
Instead of adding all these things to openlibm.

Then, we have:

• openlibm == musl fork
• openlibm-test == libc-testsuite fork

---

@ViralBShah
Another thing I am thinking about is after julia removes its dependency on openlibm (and then links to the system libm by default), would it be more useful to have a libm written by julia than to continue to improve the precision of openlibm?

[ViralBShah]

It's a good idea to have a separate repo for the tests. Julia almost has no dependency on openlibm, except in a few cases where LLVM on win32 needs it for a couple of things.

If the tests are in a separate repo, we can recreate a libm from Julia and then use the testsuite to test the Julia implementation.